When Tom Leifield steps onto the brand-new parking lot of Missouri's youngest state park, he knows he has a winner.

Once finished, the Columbia Bottom site will draw people from miles around, because this is the point where the Missouri River ends its 2,300-mile journey and flows into the mighty Mississippi. So why is Mr. Leifield, the park manager, thinking about removing the levee and letting the place flood regularly?

"We know [the park] is going to attract a lot of people, so that's going to require roads, parking lots, facilities," he says. "But we also know from a natural-resources point of view that we sort of owe it to the river to set the levee back. So we are torn."

It's a dilemma shared all along the lower Missouri. Reshaped and shored up 50 years ago, the river was engineered as a barge channel. Now, an unlikely mix of river users is coming together to push back the clock and return America's second-largest river to a more natural state.

A river, especially one as long and diverse as the Missouri, winds through so many lives and businesses that complete compromise looks a long way off. Even so, the environmental consensus already achieved here on the Midwestern plains bodes well for rivers around the country.

"Reconnecting rivers with their flood plains is an issue that's generic in the United States," says Ray Arvidson, professor of earth and planetary sciences at Washington University in St. Louis. "If you can do it on the Missouri, you can do it practically anywhere else."

Three faces of a river

Actually, the Missouri presents three faces to the world as it wends its way through eight states with enough capacity to flood four of them ankle-deep in water. From its start at Three Forks in western Montana, the river is wild and natural, relatively untouched except for a few dams and sportsmen who come for some of the best trout fishing in the country. At Fort Peck in the eastern part of the state, the river becomes a huge reservoir, held back by the first of six federal dams, which pump out hydroelectric power. After the last federal dam at Yankton, S.D., the river flows free again until Sioux City, Iowa, where it becomes a channel carrying barges to and from the Mississippi River.

The system works well from an engineering perspective. The dams produce cheap electricity, tame spring floods, and keep the barge channel open during the dry summer and fall when river levels would drop. Cities draw their water from it. Industry cools its factories with it. On its manmade lakes, fishermen float their boats.

In environmental terms, however, the Missouri is becoming a disaster. One-fifth of the river's native fish and wildlife species are on federal and state watch lists. Two shorebirds (the least tern and piping plover) and one fish (the pallid sturgeon) have declined so much that the federal government considers them endangered.

"For the last 50 years, the Missouri's been managed to keep navigation on the river," says Chad Smith, regional representative for American Rivers, a conservation group based in Washington, D.C. "And if we continue that, there's going to be species that become extinct.... It's time to change that."

Strangely enough, three forces are converging to force that change: a natural disaster, a federal law, and a historical anniversary. A decade ago, the Missouri River basin entered a prolonged drought. As the water dwindled, diverse interests began to fight over the remaining supply.

Who gets the water?

Recreation interests on the upper Missouri wanted to keep the water in the reservoirs. Commercial shippers wanted it released downstream for the barge channel. The operations manual of the US Army Corps of Engineers, which runs the federal dams, gave priority to navigation. The water flowed downstream and the upstream marinas and others began to scream. Public boating ramps were left high and dry. Marina owners found the shore had retreated up to a mile from their docks.

Governors in the affected states got so many complaints they began to lobby for changes in the Corps' procedures. Later, governors in all eight states formed the Missouri River Basin Association, which, with an additional representative for the more than two dozen native American tribes in the basin, began to look at finding ways river users could come together and agree.

The great flood of 1993 broke the drought and eased immediate pressure for change. But the Corps faced another challenge: the federal Endangered Species Act. Several species face decline because people changed the river's course, its speed, even its temperature. Environmentalists worry about the lower third of the Missouri, in particular. Manmade levees hold the water in for barge traffic. But they also keep the water from overflowing naturally into the adjacent flood plain. The result: Some kinds of fish can't spawn because they don't have shallow, slow-moving water.

That doesn't make the Missouri lifeless. But "you sort of have a monoculture of habitats," says Bill Mauck, director of the Columbia Environmental Research Center of the US Geological Survey.

Ironically, the 1993 flood helped the environmentalists' cause. The rushing water weakened and breached so many levees that many of the smaller, private ones were never rebuilt. That has rejuvenated the flood plain in places. And the US Fish and Wildlife Service is trying to secure some of that privately owned land to keep it that way.

The effort has gotten a big funding boost, thanks to the basin association. It persuaded the various river interests to back such conservation efforts. As a result, Congress agreed to increase its appropriation for land acquisition from an initial $1.5 million to $8 million a year.

Shifting alliances

"We were amazed at what things we could agree on," says Richard Opper, the group's executive director. Upstream recreation groups have stopped calling for an end to commercial navigation on the lower Missouri. Farm and even navigation groups rallied around the government land buyout program.

The most contentious issue - the timing and size of water releases from the Corps' dams - remains unresolved. Environmentalists want big releases during the spring (to mimic nature's wake-up call to wildlife), but water held back during the summer. Letting river levels fall would expose river sandbars favored by some bird species. Farmers worry that large spring rises could flood their river-bottom fields and keep them from planting.

Towboat captains don't want to give up the summer shipping season. Even though tonnage shipped on the Missouri has dwindled dramatically in the last 20 years and represents less than 1 percent of the cargo carried on the Mississippi, navigation has powerful allies. River cities depend on the Missouri for drinking water; factories use it for cooling; farmers like the competition barges offer to truck and rail.

"It's a matter of assuring access to another mode of transportation," says Dan Cassidy, director of national legislative programs for the Missouri Farm Bureau in Jefferson City, Mo.

This month the various interests will meet again to try to hammer out a compromise. The Corps has offered eight alternatives to its current management procedure. Participants remain cautiously optimistic. "We're hopeful that we'll come out of this with something that's advantageous or acceptable to all the various users," Mr. Cassidy says.